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“Children who go to nursery are 50% more likely to be overweight than those cared for by their parents”, reports the Daily Mail in a rare example of a newspaper headline underplaying the health risk found in research.

The news is based on a Canadian study which followed children from 1.5 to 10 years old and found they were 65% more likely to become overweight if cared for in a nursery-style setting, than those cared for by a parent, and who had little exposure to other forms of childcare.

However, this interesting study raises more questions than it answers. It is unclear why childcare arrangements would be associated with weight gain, and the study cannot show a cause and effect relationship between centre-based childcare and obesity. The researchers speculate that some childcare centres may have ‘obesogenic’ features (those that promote weight gain).

It’s also worth bearing in mind that the study was performed in Canada, and it may be that the results cannot be translated to the UK, or other countries.

However, it serves to highlight the importance of good diet and plenty of physical activity for all children, regardless of where they are looked after.

Where did the story come from?

The study was carried out by researchers from institutes in England, Ireland, France and Canada. It was funded by the Ministère de la Santé et Services sociaux du Québec (Québec Government’s Ministry of Health and Social Services), the Fonds de recherché en santé du Québec, and Canada’s Social Science and Humanities Research Council.

The research was covered by the Daily Mail, which reported that children who go to nursery are 50% more likely to be overweight than those cared for by their parents. However, the research actually found that children who go to nursery have a 65% increased chance of being overweight in later childhood. Which, as mentioned, is a rare example of a newspaper headline underplaying a health risk found in research.

The Mail’s coverage also rather crassly plays on parents’ fears with the introduction, ‘If working parents didn't feel guilty enough about leaving their children at nursery, now new research has found daycare could encourage obesity’.

What kind of research was this?

This was a prospective cohort study. It aimed to determine whether there was an association between childcare arrangements when children were 1.5 to 4 years old and overweight/obesity between 4 and 10 years of age.

This is the ideal study design to address this question. However, it cannot show that childcare arrangements are responsible for any association seen (a cause and effect relationship) as there may be other unmeasured confounding factors involved, such as a family’s diet and activity levels.

What did the research involve?

The study enrolled 1,649 children born between October 1997 and July 1998 in Quebec, Canada. Their mothers completed questionnaires about their childcare arrangements when the children were aged 1.5, 2.5, 3.5, and 4 years old. The mothers were asked if their child was attending, and for how many hours per week, childcare:

in someone else’s home, care by a non-relative (family-based childcare)

own home, care by a non-relative (care by a nanny/babysitter)

someone else’s home, care by a relative (care by a relative)

own home, care by a relative other than a sister or brother (care by a relative)

own home, care by a sister or brother (care by a relative)

care in a daycare centre (centre-based childcare)

other

The researchers included childcare arrangements that occurred for at least 10 hours a week. When the children were aged 4, 6, 7, 8 and 10 years old, their height and weight were measured so that their body mass index (BMI) could be calculated. Children were classified as normal weight, overweight, or obese.

The researchers then looked to see if there was an association between the main childcare arrangements when the child was 1.5 to 4 years old and if the child became overweight or obese. The researchers attempted to adjust for a variety of factors that could explain any association seen (confounders), including:

birth weight

smoking during pregnancy

whether the child was breastfed

the mother’s BMI

whether the mother was employed

whether the mother was depressed

family functioning

maternal overprotection

the child’s ethnic background

socioeconomic status

What were the basic results?

After adjusting for potential confounders, the researchers found that:

Children who attended centre-based childcare had 65% increased odds of being overweight or obese compared to children cared for by a parent, who had never had more than 10 hours a week of exposure to another form of childcare (odds ratio [OR] 1.65, 95% confidence interval [CI] 1.13 to 2.41).

Care by a relative was also associated with increased risk of being obese compared to care by a parent, but this association was not statistically significant (0.95 to 2.38) – so it could have been the result of chance.

There was no association between family-based childcare and nanny/babysitter care and children’s overweight/obesity over the six-year follow-up period.

When the researchers looked at the amount of time spent in childcare, they found that each block of five hours spent in either centre-based childcare or being cared for by a relative, increased the odds of being overweight or obese in childhood by 9%.

How did the researchers interpret the results?

The researchers concluded that “overweight/obesity was more frequently observed in children who received non-parental care in centre-based settings or care by a relative other than a parent.

‘Obesogenic’ features of these childcare arrangements should be investigated in future studies.”

Conclusion

This Canadian study found that children who were mainly cared for by centre-based childcare between the ages of 1.5 and 4 had greater odds of being overweight or obese in childhood (from 4 to 10 years of age) than children cared for by a parent (who had never had more than 10 hours a week exposure to another form of childcare).

This was a well designed study, and included a large number of children whose childcare arrangements and BMI were repeatedly measured. However, this study design cannot show that the childcare arrangements were responsible for children being overweight or obese (a cause and effect relationship).

Although the researchers adjusted for a number of factors that could explain the associations seen (confounders), other factors could still be responsible for these associations. For example, while they adjusted for the mother’s BMI, they didn’t examine the diet and physical activity patterns of the child and their parents. These types of factors are likely to be having a direct influence on the child’s weight.

There was also no attempt to investigate the levels of physical activity or quality of the diet provided at the various childcare centres.

As the researchers report, the association between childcare arrangements and obesity has been investigated previously, albeit inconclusively, as not all studies have found the same result.

The researchers speculate that “differences in the quality or regulation of childcare centres with respect to nutrition and physical activities”, might explain the differences in results. They conclude by recommending that further research is undertaken to more thoroughly investigate the possible association between childcare centres and increased risk of weight gain.